1. Field of the Invention
The present invention relates to a key structure which is applied to a key having a wood part.
2. Description of the Related Art
Conventionally, key structures are known which function as a key pivotally moved by key depression and employ a wood part made of wood or the like as a part thereof, as disclosed in Japanese Laid-Open Patent Publications (Kokai) No. 2003-271127 (hereinafter referred to as the key structure according to first prior art) and No. 2003-271128 (hereinafter referred to as the key structure according to the second prior art). In such woody key structures, the wood part is provided at least for a so-called “visible part” which is visible from the outside during both performance and non-performance, so as to cause the key structure to present a woody appearance and a high-quality appearance. In the woody key structures, the wood part is supportably fixed e.g. using an adhesive to the lower surface of an upper plate body made of synthetic resin and having a playing or depressing surface, and to the upper surface of a key base body made of synthetic resin. The upper plate body and the key base body have elongated shapes corresponding to the shape of the key, and these support members and the wood part form the key structure.
However, the above key structures according to the first and second prior arts suffer from the following problem: The base end of the key base body is not in contact with the wood part in the longitudinal direction of the key structure, that is, each of the key structures has a clearance provided between the base end of the key base body and the wood part and extending transversely of the key structure, for accommodating a dimensional change due to an environmental change, such as changes in temperature and humidity, or a manufacturing error, and therefore the wood part is placed in a state supported only by the key base body in the vicinity of the clearance. This causes concentration of stress in the key base body in the neighborhood of the clearance e.g. when the key is depressed, which makes the wood part liable to separation from the key base body. Further, the whole key structure has low flexural rigidity.
Therefore, the conventional key structures still remain to be improved in durability and accuracy by preventing separation between the wood part and the key base body from being caused e.g. by key depression, and increasing the rigidity of the key structure. Particularly from the viewpoint of enhancement of the rigidity of the whole key structure, it is desired that not only the properties of the wood part which is deformed due to an environmental change, but also the properties of the synthetic resin-made upper plate body and key base body which are deformed due to molding thereof should be considered comprehensively.